In answer, I'll quote Wayne Goddard....
A knife MUST:
1. Look good
2. Feel good
3. Work good
Wayne told me that MANY years ago, and at first I thought it was just a quick answer to placate a young kid (me). But as time went by, I realized that Wayne had summed up the qualities of a knife in simple, straight forward terms, with a great deal of meaning.
My personal thoughts on each of those areas are:
Look Good: In order to attract a customer, the knife must grab their attention, that doesn't mean that it has to be something odd or different, just that all the parts must be in the right place, with correct dimensions, lines, and flow for the given knife.
Feel Good: Once a knife grabs someones attention, the very next thing they want to do is pick it up and handle it. The overall feel, balance and fit must be correct for a given knife to "feel good" in the hand.
Work Good: This is the one aspect that a customer cannot determine immediately upon purchasing a knife, but it is something that you as the maker MUST ensure through research, experimenting, and testing.
The first two areas will bring people to your knives, but it is you, as the maker, who must ensure that the knife will "work good". That is the part of the equation that that will make your customer a happy one, or will spread your reputation as a maker who makes a nice looking knife that doesn't "work" very well.
After all these years of making knives, I still find myself surprised that many makers have learned how to incorporate the first two elements, yet have paid little or no attention to the third, and what I consider the most important element.
I don't say that to belittle anyone, but rather in hopes of helping others see how important the "work good" aspect is in the knives they make. The work good aspect only comes from a maker testing and using the knives they make, taking the time to understand the relationships between heat treating and geometries, and in general, paying attention to those things that cannot be seen with the naked eye.